In a statement on Wednesday morning the Basel public prosecutor said they had arrested a 41-year-old Albanian citizen “who is strongly suspected of being involved”. He has been placed in custody for three months.

Speaking to 20 Minuten, a commissioner from the Basel prosecutor's office said the arrest took place sometime in the last few weeks but would not say precisely when, for reasons related to the investigation.

A second suspect is still on the run.

The motive for the shooting has not yet been established and is the subject of a “difficult and extensive” investigation, said the prosecutor's statement.

Any link to drugs, as reported in Swiss media, has not yet been clarified.